How hard is it to call a cell phone?

I don't know why, but so many of the contractors we have worked with don't get the idea of "call me on my cell phone at ###-###-####." Sometimes I call from my home phone because of better reception and to save minutes, but I always say "call me on my cell phone at ###......" In fact, I usually even say, "this is my home number I'm calling from, and since I'm not always here please call me back on my cell phone at ###-" I cannot tell you how hard this has been for so many people we have worked with. It really doesn't seem that difficult a concept to me, but it must be difficult for some people. I had one contractor who preferred to communicate by text, and I tried and tried and could not get him to text my cell phone. He insisted on texting my computer and then I wouldn't get his messages for hours. I can't tell you how much time this wastes. I don't get what is so hard about this concept.